linux-kernel - Re: [PATCH v2 3/3] bcache: Remove unnecessary select MIN

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Message-ID: <d45nj54fidgmxfjryx42tuaddwkjeogq2zb2i3oki7rstdeut6@obcycu7j4igw>
Date: Sun, 15 Jun 2025 13:52:01 +0800
From: Coly Li <colyli@...nel.org>
To: Kuan-Wei Chiu <visitorckw@...il.com>
Cc: akpm@...ux-foundation.org, kent.overstreet@...ux.dev, 
	robertpang@...gle.com, linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org, 
	jserv@...s.ncku.edu.tw, stable@...r.kernel.org
Subject: Re: [PATCH v2 3/3] bcache: Remove unnecessary select MIN_HEAP

On Sun, Jun 15, 2025 at 04:23:53AM +0800, Kuan-Wei Chiu wrote:
> After reverting the transition to the generic min heap library, bcache
> no longer depends on MIN_HEAP. The select entry can be removed to
> reduce code size and shrink the kernel's attack surface.
> 
> This change effectively reverts the bcache-related part of commit
> 92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap
> API functions").
> 
> This is part of a series of changes to address a performance
> regression caused by the use of the generic min_heap implementation.
> 
> As reported by Robert, bcache now suffers from latency spikes, with
> P100 (max) latency increasing from 600 ms to 2.4 seconds every 5
> minutes. These regressions degrade bcache's effectiveness as a
> low-latency cache layer and lead to frequent timeouts and application
> stalls in production environments.
> 
> Link: https://lore.kernel.org/lkml/CAJhEC05+0S69z+3+FB2Cd0hD+pCRyWTKLEOsc8BOmH73p1m+KQ@mail.gmail.com
> Fixes: 866898efbb25 ("bcache: remove heap-related macros and switch to generic min_heap")
> Fixes: 92a8b224b833 ("lib/min_heap: introduce non-inline versions of min heap API functions")
> Reported-by: Robert Pang <robertpang@...gle.com>
> Closes: https://lore.kernel.org/linux-bcache/CAJhEC06F_AtrPgw2-7CvCqZgeStgCtitbD-ryuPpXQA-JG5XXw@mail.gmail.com
> Cc: stable@...r.kernel.org
> Signed-off-by: Kuan-Wei Chiu <visitorckw@...il.com>

Acked-by: Coly Li <colyli@...nel.org>

Thanks.


> ---
>  drivers/md/bcache/Kconfig | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/md/bcache/Kconfig b/drivers/md/bcache/Kconfig
> index d4697e79d5a3..b2d10063d35f 100644
> --- a/drivers/md/bcache/Kconfig
> +++ b/drivers/md/bcache/Kconfig
> @@ -5,7 +5,6 @@ config BCACHE
>  	select BLOCK_HOLDER_DEPRECATED if SYSFS
>  	select CRC64
>  	select CLOSURES
> -	select MIN_HEAP
>  	help
>  	Allows a block device to be used as cache for other devices; uses
>  	a btree for indexing and the layout is optimized for SSDs.
> -- 
> 2.34.1
> 

-- 
Coly Li